Ultrasonic diagnosis devices used in the field of medicine generally include a main unit (a cart), and an operation panel supported on the main unit. The main unit houses a plurality of electronic circuit boards and power source sections. The operation panel includes a switch, a pointing device, a rotary knob, a sub display, or the like. A display unit is mounted on the operation panel via an arm mechanism. In such a structure, the operation panel, the arm mechanism, and the display unit constitute a movable section. The display unit may be mounted directly on the main unit, rather than via the operation panel.
As disclosed in Patent Literature 1, an arm mechanism generally includes a plurality of pivot mechanisms and a plurality of arms. The arm mechanism further includes a tilt mechanism. A member having sufficient rigidity is used as each of the members forming the arm mechanism. Further, the arm mechanism is configured such that backlash is minimized in coupling portions between the members.